Switch employing damping means for controlling movement of its bridging elements



June 16, 1959 M, RAMRATH 2,891,134

SWITCH EMPLOYING DAMPTNG MEANS FOR coNTRoLLTNG MOVEMENT oF' ITs BRTDGING ELEMENTS Filed Dec. 5. 1956 nite States Patent Patented June 16, 1959 Joseph M. Rami-ath, Mattapan, Mass., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis.

applicati@ December s, 1956, serial No. 626,429

9 claims. (cl. zoo-.170)

This invention relates to electric current interrupters and more particularly to a new and improved switch employing contact damping means.

It is well known in the art of electric circuit interrupters that if cooperating separable contacts are rigid metallic elements any appreciable misalignment between the contact surfaces due to inaccuracies of manufacture or assembly or due to wear results in unequal pressure distribution throughout the contact surface and in extreme conditions single point contact. In oil circuit breakers the contacts are subject to thermal and dynamic stresses in keeping with the high circuit breaker ratings and high speed switch operations. In order to withstand the high inrush current under short circuit conditions and to insure equal current distribution throughout all of the contact elements to avoid pitting of the contact surfaces a great number of contact points must be made. Experience has taught `that the lower limit of the Width of finger contacts is about of an inch. If a plurality of nger contacts of this width are to be used to constitute the connecting means in a blade nger contact structure, springing of the fingers becomes a problem. Another diiculty encountered is the repulsive force that tries to push the contact fingers apart when the blade is brought into engagement with the fingers at closing in on short circuit. This difficulty is increased b y the mechanical movement of the blade at high closing speeds resulting in a mechanical throwoff force of the lingers. The combination of the repulsive force and the throwoff force of this type of contact structure may cause severe burning of the contact surfaces and after a few operations result in the destruction of the contact structure.

. In accordance with the invention claimed a new and improved electric switch structure is provided comprising a` pair of cooperating relatively movable Contact elements each having a contact surface and a plurality of rigid conducting bridging elements. The bridging elements are disposed to engage the surfaces of the contact elements in circuit closing position of the switch. Spring biasing means are disposed to bias the bridging elements into engagement with the contact elements and a resilient mat is interposed between the spring biasing means and the bridging elements for procuring substantially equal contact pressure at all points of contact during switch closing operations by damping the movement of the bridging elements.

It is, therefore, one subject of this invention to provide a new and improved electric switch.

I Another object of this invention is to provide a new and improved electric switch employing a plurality of linger contact elements in which substantially equal contact pressure is provided at all points of contact during switch closing operations by damping the movement of the bridging contact elements.

.l A further object of this invention is to provide a new and improved switch employing separable contacts which is substantially unaffected by the forces occasioned by short circuits or substantial overloads in a circuit in which the switch is connected.

A still further object of this invention is to provide a new and improved circuit interrupter which is simple, reliable and ilexible in operation, rugged in structure and economical to manufacture.

Objects and advantages other than those set forth will be apparent from the following description when read in connection with the accompanying drawing, in which:

Fig. l is a front View in cross section of a switch structure taken along the line I-I of Fig. 2 and embodying the invention;

Fig. 2 is a cross sectional right end View of the structure shown in Fig. 1 taken along the line II-II; and

Fig. 3 is a cross sectional IView of Fig. 1 taken along the line III- IIL Referring more particularly to the drawing by characters of reference, Figs. l, 2 and 3 illustrate an electric switch 10 comprising a U-shaped relatively stationary current conductive contact 11 and a cooperating movable current conductive contact 12. The U-shaped stationary contact 11 comprises a pair of legs 13 and 14 which may be, for example, parallelly arranged and interconnected by a bight 15 dening a protrusion 16. Protrusion 16 extends from bight 1S between legs 13 and 14 for supporting a pair of, for example, parallelly arranged opposed contact surfaces 17. The movable contact 12 is provided with a projecting blade having a pair of,

` for example, opposed parallelly arranged contact surfaces 18. The contact elements 11 and 12 are normally symmetrical about a common plane including their longitudinal axes.

Supported from the legs 13 and 14 of' the stationary contact 11 are a pair of side members 19 and 20 secured thereto by suitable bolts 21 extending from end plates 30 and 31. The stationary contact 11 and its side members 19 and 20 combine to form a rigid boxlike structure for enclosing the movable parts of switch 10. Extending between legs 13 and 14 one on each side of protrusion 16 and arranged substantially parallel with side members 19 and 20 are a pair of pivot pins 22 and 23 upon which are disposed or mounted a plurality of rigid conducting bridging elements 24. Bridging elements 24 are provided with arcuate contact surfaces near each end of each element and so disposed, as illustrated in Fig. 1, when in switch closed position to engage edgewise the opposing contact sur-faces 117 and 18 of contact elements 11 and 12, respectively. The bridging elements 24 may be punched blades or laminations or any suitable rigid conducting elements.

The opposed finger contact members or bridging elements 24 are biased toward each other and protrusion 16 and thus into pressure engagement with the opposed contact surfaces of the contact elements 11 and 12 by suitable biasing means such as springs 25. Springs 2S are each disposed between one of the legs of the U- shaped contact element 11 and protrusion 1 6 and areeach loosely arranged within a diiferent aperture 26 formed in the juxtapositioned surfaces of side members 19 and 20. The position and manner in which these biasing springs are assembled is shown in detail in Figs. l, 2 and 3. Springs 25 are given suitable compression by means of end plates 30 and 31 and bolts 21.

In accordance with the invention claimed resilient mats 27 of suitable material such as rubber or plastic are interposed between the springs 25 and the bridging ,ele-

ments 24 on each side of protrusion 16. Each mat 27 is fastened tol a diiferent one of the side members 19 and 20 by bolts 28 at the ends thereof adjacent to proytIiJsion 16, and form by reason of the resiliency of the mat a pivotal connection. The purpose of mats 27 is to establish `a uniform pressure over the current carrying bridging fingers or elements 24, making use of the snenginess cf. the rubberlike material to 'F111 in any uni evenness of the Surface formed by the back edges of the bridging elements. Mats 2,7 also act as a means to provide ample damping of the movement of the bridging elements during a switch closing operation.

I f switCh 1,0, is used in a bath of iluid such as oil and the Switch is closed by blade 12 wedging in between bridging elements 24, oil trapped under mats 27 may leave only at the lower or open end of the switch, as shown in Eig. 1. Mats 27 as shown in Fig. 3 are wide enough to extend completely across the back of the bridging elements and .oil trapped between mats 27 and side members 19 and 20 by reason ofthe fact that mats 21 are heldl away from legs 13 and 1,4 a predetermined distance at their free'ends by springs 25 is forced out from between mats 27 and legs 13 and 14 by the outward movement of the bridging elements 24 during a switch closing operation. The oil dampens the outward movement of the bridging elements to prevent the bridging elements 24 from losing contact with the movable contact 1,2 during contact opening 1' closing operations. In this manner the springing movement of the bridging elements is greatly reduced or satisfactorily controlled. Also, the difficulty encountered by the repulsive forces pushing the bridging elements away from the movable blade contact 12 when closing the switch on a shorted circuit is damped or controlled by the switch structure described and claimed.

11.1. order. te eentrel the inward movement ef the bridging, elements 24. during a switch opening operation and to retain the lower ends of the` bridging elements apart a predetermined ydistance in switch open'position each bridging element ie. Prende@ with. e Surface 2.9 fer aber ting the side members 19 or'20 depending on which side otrprotrusion 18 the bridging element is mounted. Thus, as the switch opens springs 2,5Y bias the opposing bridging elements toward each otherand they move toward each other until vsurfaces 29 engage side members 19 and 2i).

When switchV 1G is closed by the wedge movement of contact element 12 between the bridging elements 24 the bridging"elements are pivotedaway from contact element 1,2 forcing oil or air,`dep`e`nding onl the medium in which` it operates, out from.` under mats 27. The bridging elements "because ofl the damping action cling tof-the movable contact element 12, thus eliminating severe burningof the Contact surface usually occurring with switches not provided 4with 'a suitable bridging elc- Itie'nt damping rneans. i 'Y `VWhile the invention has been applied. to a switchf structure employing afplurality of pairs: olf/opposed bridging elements 24, it will, be' apparent 'that' anyy desired'V number of bridging elementsfrnay bev'employed.v anddispose'd on one or both sides of thestationaiyfcontact.

Although but one. embodiment of the present inventionY has been illustrated and` described," it will be apparent to those skilled in the. art that various changes and modicatio-ns may be made herein without departing. fromthe spirit of the invention or from the scope of the appended claims, Y

4What is claimedis:

l`. In' an electric switch the combination comprising aA pair' of Cdoperat-ing`v `relatively movable! contact ele` ments each lravlir'rgf contactY surfaces, a` plurality` of rigidi conducting bridging elements, said elements beingfdisposedto engagen saids 'rfaces of said contact elements circuit closing position/of said switcligspring biasing means disposed tof bias said? bridging elements into errgagemen't with saidv Contact elements, and a? resilient` mat secured at olie end `to one of'saidf contact elements and interposed along its length between said spring biasing means'aud saidbridging elements for procuring sub# 4 stantially equal contact pressure at all points of contact during switch .closing operations by damping the. movement of said bridging elements.

2. In an electric switch the combination comprising a pair of cooperating relatively movable contact elements each having opposed contact surfaces, a plurality of pairs of rigid conducting bridging elements, the elements of each pair being disposed to engage opposing surfaces of said contact elements in circuit closing position of saidy switch, spring biasing means disposed to bias .said bridging elements into engagement with said contact elements, and a resilient mat secured at one end to yone of said contact elements and interposed along its length between said spring biasing means `and said bridging elements for procuring substantially equal Contact pressure at all points of contact during switch closing operations by damping the movement of said bridging elements.

3.. In .an electric switch the combination comprising a U shaped relatively stationary contact element and a cooperating relatively movable contact element each hav.-1 ing contact surfaces, said U-shaped contact element; comprising. a pair of spaced legs interconnected by a. bight and defining `a protrusion extending from Said. bight be, tween. said. legs. for supporting Said eentaet Surfaces en. said stationary contact, a plurality of.l rigid condnctging. bridging elements, said elements being disposed between Said. leas t0 engage Said Surfaces. ef. Seid; U-Sheped een: tact element and. Seid Surfaces Of Said meveble eetltaet element in circuit closing position of said switch, spring, biasing means disposed between one of said legs and said protnusion to bias said bridging elements into en-A sagement. with. said Stationary eenteet element and Sel@ movable contact element, and a resilient mat interposed between. Seid. Spring biasing. means and Seid. bridging ele; ments. for procuring substantially equal Contact pressure; at ally points of contact during switch closing opera'tions.v by damping the movement of`said bridging elementsg 4. In an electric switch the combination comprising ai tJ-shaped relatively stationary contact element and a cooperating relatively movable Contact element each having opposed 4contact, surfaces, said U-shaped contact element comprising a pair of spaced legs interconnected by a bight and deining a protrusion extending from bight between said legs for supporting said opposed/conf tact surfaces on said stationary contact, a pair. .of rigid conducting bridging elements, said elements being. Vdisposed between said legs one on each side of saidiprot'r'usion fori-engaging opposing surfaces of said Ushaped element and said movable element in circuit closing positionv of said switch, a pair of spring biasing means each. disposedA between one of said legs and said protrusion't bias said bridging( elements into engagement said stationary contact element andl said. movable contactv ele'-, ment,v and a Vpair ofl resilient mats one interposed between each'of said spring biasing means andi said'bridging e ments on a different side of said. protrusion.` for procuring. substantially equal (,:ontact'pressur'ey at all points. of contact,Y during switch closing operations. by. dampingV the. Inova ment'of said bridging elements.

`5. In an electric switch the combination comprising a U-shaped relatively stationary contactV element` and? af.` cooperating relatively movable contact.elementy eachh'av.- ing opposed contact surfaces, said U-shaped contactelement comprising aipair of spaced legs interconnected bya bignt andA defininga protrusion extending from said bi'ght between said legs forsupporting said4 oppos'efdcontact' surfaces on said stationary contact, 'a' pair fof rigidfcon ducting bridging elements, said elements being" disposed` between said legs one on each side of said prot'rusion for" engaging opposing surfacesof said U-shaped contactele'` ment` and said movable contact element` in circuitclosing? position` ofsaid switch, a pair of springbiasingmeans' each disposed between one of saidlegs and said protrusion to bias said bridging elements into. engagementwithsaid stationary contact element and said movable contact element, and a pair of resilient mats each pivotally mounted at one end thereof to a different one of said legs and interposed between said spring biasing means and said bridging elements for procuring substantially equal Contact pressure at all points of contact during switch closing operations by damping the movement of said bridging elements.

6. In an electric switch the combination comprising a U-shaped relatively stationary contact element and a cooperating relatively movable contact element each having opposed contact surfaces, said U-shaped contact element comprising a pair of spaced parallelly arranged legs interconnected by a bight and defining a protrusion eX- tending from said bight between said legs for supporting said opposed Contact surfaces on said stationary contact, a plurality of pairs of rigid conducting bridging elements, the elements of each pair being disposed between said legs one on each side of said protrusion for engaging opposing surfaces of said U-shaped contact element and said movable contact element in circuit closing position of said switch, a plurality of spring biasing means each disposed between one of said legs and said protrusion to bias said bridging elements into engagement with said stationary contact element and said movable contact element, and a pair of resilient mats` one arranged on each side of said protrusion and interposed between said spring biasing means and said bridging elements for procuring substantially equal contact pressure at all points of contact during switch closing operations by damping the movement of said bridging elements.

7. In an electric switch the combination comprising a U-shaped relatively stationary contact element and a cooperating relatively movable contact element each having opposed contact surfaces, said U-shaped contact element comprising a pair of spaced parallelly arranged legs interconnected by a bight and defining a protrusion extending from said bight between said legs for supporting said opposed contact surfaces on said stationary contact, a plurality of pairs of rigid conducting bridging elements, the elements of each pair being disposed between said legs one on each side of said protrusion for engaging opposing surfaces of said U-shaped contact element and said movable contact element in circuit closing position of said switch, a plurality of spring biasing means each disposed between one of said legs and said protrusion to bias said bridging elements into engagement with said stationary contact element and said movable contact element, and a pair `of resilient mats each pivotally mounted at one end thereof to a diierent one of said legs and interposed between said spring biasing means and said bridging elements for procuring substantially equal contact pressure at all points of contact during switch closing operations by damping the movement of said bridging elements.

8. In an electric switch the combination comprising a U-shaped relatively stationary contact element and a cooperating relatively movable contact element each having opposed contact surfaces, said U-shaped contact element comprising a pair of spaced parallelly arranged legs interconnected by a bight and defining a protrusion extending from said bight between said legs for supporting said opposed contact surfaces on said stationary contact, each of said legs defining a plurality of apertures arranged in their juxtapositioned surfaces, a plurality of pairs of rigid conducting bridging elements, the elements of each pair being disposed between said legs one on each side of said protrusion for engaging opposing surfaces of said U-shaped contact element and said movable contact element in circuit closing position of said switch, a plurality of springs each arranged within a different one of said apertures and between one of said legs and said protrusion to bias said bridging elements into engagement with said stationary contact element and said movable contact element, and a pair of resilient mats each pivotally mounted at one end thereof to a ditferent one of said legs and interposed between said springs and said bridging elements for procuring substantially equal contact pressure at all points of contact during switch closing operations by damping the movement of said bridging elements.

9. An electric switch for operation within a fluid comprising in combination a U-shaped relatively stationary contact element and a cooperating relatively movable contact element each having opposed contact surfaces, said U-shaped contact element comprising a pair of spaced parallelly arranged legs interconnected by a bight and dening a protrusion extending from said bight between said legs for supporting said opposed contact surfaces on said stationary contact, a plurality of pairs of rigid conducting bridging elements, the elements of each pair being disposed between said legs one on each side of said protrusion for engaging opposing surfaces of said U-shaped contact element and said movable contact element in circuit closing position of said switch, a plurality of spring biasing means each disposed between one of said legs and said protrusion to bias said bridging elements into engagement with said stationary contact element and said movable contact element, and a pair of resilient mats each pivotally mounted at one end thereof to a different one of said legs and interposed between said spring biasing means and said bridging elements, said mats being held away from said legs a predetermined distance at their free ends by said spring biasing means whereby during switch closing operations said mats force fluid out from between said mats and said legs to damp the outward movement of said bridging elements to prevent said bridging elements from losing contact with said movable contact element.

References Cited in the file of this patent UNITED STATES PATENTS 547,537 Biddle et al. Oct. 8, 1895 2,356,069 Leitzel et al. Aug. 15, 1944 

